DOWNSTREAM MOVEMENT OF LAMPREYS AND FISHES 

 IN THE CARP LAKE RIVER, MICHIGAN 



An inclined -screen trap was first installed 

 near the mouth of the Carp Lake River, Emmet 

 County, Michigan in the spring of 1948. The de- 

 vice has been in nearly continuous operation since 

 that time. Detailed reports of the construction 

 and operation of this trap and of the downstream 

 movement of recently transformed sea lampreys, 

 Petromyzon marinus, in this river in the 1948-49, 

 1949-50, and 1950-51 seasons have been present- 

 ed by Applegate (1950) and Applegate and 

 Brynildson (1952). 



The purpose of this report is to present a sup- 

 plemental record of the downstream movement 

 of lampreys in this river in the seasons of 1951-52 

 through 1957-58 and to summarize the records of 

 fishes captured in the trap during the entire per- 

 iod of operation. 



Studies of the downstream runs of recently 

 transformed sea lampreys and of larval lampreys 

 'n the CariJ Lake River since 1952 generally sub- 

 stantiate the data presented by Applegate and 

 Brynildson (1952). In the following discussions 

 of the tabular data given here, comment is made 

 only where the years of additional records have 

 provided a better understanding of some features 

 of the migration. 



DOWNSTREAM MOVEMENT OF LAMPREYS 



During the 10 annual migratory seasons be- 

 tween the summer of 1948 and that of 1958, 

 74, 299 transformed or partly transformed sea 

 lampreys, 847 adult brook lampreys ( Lampetra 

 lamottei ), 27 adult silver lampreys (Ichthyomyzon 

 unicuspis) , and 72, 979 larval lampreys of several 

 species were captured in the trap. The numbers 

 of each species and life -history stage taken in each 

 year are summarized in table 1. 



Certain groupings of the data in table 1 re- 

 quire explanation. Beginning with the 1953-54 

 season, no further effort was made to distinguish 

 between transformed and partly transformed sea 

 lampreys. The latter comprise such a small por- 

 tion of the total run in any year that their separa- 



tion after the first 5 years served no useful purpose. 

 At the start of these studies, no entirely reliable 

 means existed of distinguishing between the larvae 

 of Petromyzon and Lampetra . The larvae conse- 

 quently had to be combined in all records. This 

 practice was continued after better means of identi- 

 fication became known because trained observers 

 were not available to examine each day's catches 

 in the trap. This same lack of trained observers 

 also prohibited maintenance of separate records for 

 Ichthyomyzon larvae after the 1952-53 season; the 

 numbers fortunately were few. The relatively sparse 

 numbers of adults captured of the brook and silver 

 lampreys suggest strongly that very nearly all of the 

 Icurvae taken in the Carp Lake River trap were those 

 of the sea lamprey. 



Daily records of catches of recently transformed 

 sea lampreys moving downstream during the migra- 

 tory seasons 1951-52 through 1957-58 are presented 

 in tables 2 through 8. Ecological factors such as 

 water level, water temperature, and prevailing 

 weather, are also included in these records. 



The principal features of this migration of the 

 sea lamprey are as follows: downstream movement 

 usually begins in early October, extends through the 

 winter and early spring, and ends sometime in AprQ. 

 A few scattered individuals may come downstream 

 as early as mid -September or as late as mid -May. 

 The migration is usually greatest in late March and 

 early April; a lesser peak of activity appears in Novem- 

 ber. During the intervening winter months, a few 

 come downstream nearly every day. Sudden minor 

 spurts of activity may also occur during this period. 



Nearly all movements of lampreys in the Carp 

 Lake River appear to be associated with rising or 

 fluctuating water levels. Late fall rains which in- 

 crease the flow bring down the initial surge of newly 

 transformed individuals. Flood conditions resulting 

 from midwinter thaws and rains are generally accom- 

 panied by sudden increases in downstream movement. 

 The greatest downstream migration occurs on the 

 rise and crest of the floods resulting from the general 

 spring breakup in late March or early April. For 

 this reason, the calendar dates of the migration vary 

 from year to year. 



